Pistons of internal combustion engines



Dec. 19, 1967 R.. HERRMANN I 3,358,657

P ISTONS OF INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet l Filed Deo. 23, 1965 TQQ/2].

Dec. 19, 1967 R. HERRMANN 3,358,657

PISTONS OF INTERNAL COMBUSTION ENGINES med Dec. 23, 1965 s sheets-sheet 2 Dec. 19, 1967 R.HERRMANN K 3,353,657 N PISTONS OF INTERNAL COMBUSTION ENGINES Filed Dec. 23, 1965 5 Sheets-shew*l 5 United States Patent O 3,358,657 PISTONS QF INTERNAL COMBUSTION ENGLNES Rodolphe Herrmann, Yvelines, France, assignor t Societe dExploitation des Materiels Hispano-Suiza, Bois-Colombes, France Filed Dec. 23, 1965, Ser. No. 516,069 Claims priority, application France, Dec. 29, 1964, 298 1li Claims. (Cl. 123-48) ABSTRACT 0F THE DISCLOSURE An internal combustion engine piston including a piston cap element slidable axially with respect to a piston body element, said piston elements having respective cooperating cylindrical side walls which fit slidably with respect to each other and being shaped to limit between their end walls an intermediate chamber of variable volume, for lubricating oil fed through an inlet orifice and escaping through an outlet orifice both of said orifices being formed between said piston elements, the portions of the walls of said piston elements that face each other being arranged so that when the piston cap element moves toward the piston body element under the effect of the pressure in the engine cylinder, this relative movement has for its effect to close both the inlet orifice and the outlet orifice of said intermediate chamber.

The present invention relates to pistons cooperating with cylinders and connecting rods, for internal combustion engines. Such a piston comprises a central body mounted on a connecting -rod and a sliding cap mounted on said central body and adapted to slide thereon between two given end position-s.

The central body and the sliding cap limit a chamber adapted to receive a liquid under pressure, and provided with inlet and outlet orifices. The invention is more especially, but not exclusively, concerned with pistons of this kind for internal combustion engines of the diesel type.

The chief object of the present invention is to provide a piston of this kind which is better adapted to meet the requirements of practice than those used up to this time for the same purpose.

The pressure in the cylinder varies in a periodic manner according to the engine cycle and reaches a value which will be called pilot pressure.

The liquid filling said chamber is usually the oil used for lubricating the engine. The pressure under which oil is fed to said chamber is such that when the pressure in the cylinder reaches the value of the pilot pressure the sliding cap is brought to its end position nearest to the central body.

The portions of the walls of the central body and of the sliding cap which face each other are designed in such manner that when the sliding cap is brought to its end position nearest to said central body by the pressure in the cylinder, the inlet and the outlet orifices are closed. Thus, for every cycle in the cylinder the mass of oil is kept in said chamber and permits transmission of axial forces between the sliding cap and the body.

Another feature of the present invention consists in making the central body of a light alloy and the sliding cap of a metal capable of resisting to high temperatures.

Still another feature of the present invention consists in providing the central body and the sliding cap with 3,358,657 Patented Dec. 19, 1967 ice axial guiding means made of surfaces which can be separated by grooves adapted to receive the cooling oil in circulation, whereby heating of the sliding cap is reduced.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings given merely by way of example, and in which:

FIG. l is an axial section of a piston according to a preferred embodiment of the invention, the piston structure being expanded;

FIG. 2 is a partial axial section of the piston shown by FIG. l, the piston structure being constricted,

FIG. 3 is a partial axial section of a piston according to another embodiment of the invention, the piston being expanded;

FIG. 4 is an axial lsection of the piston of FIG. 3, in constricted position of the structure;

FIG. 5 is a section on the line V-V of FIG. l;

FIG. 6 is a partial view of one of the elements constituting the piston shown by FIG. l.

The disel engine comprises a piston 1, a cylinder 2 and a cylinder head 3. Piston 1 is made of two elements, to wit, on the one hand, a body 4 having an end portion 5 and a skirt 6 mounted on a connecting rod 7 through a gudgeon pin 8 and on the other hand, a sliding cap havan end portion 10 and a skirt 11.

Sliding cap 9 is mounted slidable on body 4 between two relative end positions.

Body 4 and sliding cap 9 limit, between the outer face of the end portion 5 of body 4 and the inner face of the end portion 10 of sliding cap 9, a chamber 12 fed with a liquid under pressure P, which liquid may be the oil used for lubricating the engine.

Chamber 12 is provided with at least one inlet orifice and at least one outlet orifice, the section of the latter being such -as to keep in chamber 12 a pressure nearly equal to pressure P.

Piston 1 has five packing rings 13, three of which are carried by sliding cap 9, one of which is carried by body 4 and located between sliding cap 9 and gudgeon pin 3, and one of which is carried by body 4 and located in the lower part of the skirt 6 of body 4.

The portions of the walls of body 4 and sliding cap 9 which face each other are designed in such manner that, when sliding cap 9 is in its end position near body 4 under the effect of the pressure in the engine cylinder, both the inlet and the outlet orifices of chamber 12 are closed.

Thus, on every cycle of piston 1, a volume of oil is kept in chamber 12 and serves to the transmission of forces between body 4 and sliding cap 9, said volume of oil being partly renewed on every stroke.

According to a first embodiment of the invention, shown in FIG. l, sliding cap 9 is axially guided through the inner walls of skirt 11 and the outer walls of the upper part of the skirt 6 of body 4. Relative axial movement of sliding cap 9 away from body 4 is limited by the following means: An axial projection 14 of sliding cap 9 extending through a central bore 15 of body 4, and carrying an abutment 16 fixed thereto through a bolt 17, said abutment 16 bearing against the transverse wall of body 4.

Relative axial movement of sliding cap 9 toward body 4 is limited by providing, on the one hand, on the outer face of the end portion 5 of body 4, two annular concentric areas, one 18 immediately about central bore 15 and the other 19 at the periphery of end portion 5, and, on the other hand, on the inner face of sliding cap 9 two annular and concentric areas 20 and 21 adapted to cooperate respectively with areas 18 and 19.

Oil under pressure is fed to chamber 12 through a plurality of longitudinal slots 22 located at the periphery of the end portion of body 4.

The upper end of every slot 22 is at the level of bearing surface 19, while the lower end thereof communicates with a groove 23 of body 4.

An annular space 24 is provided between axial projection 14 and central bore 15 and is connected with orifices 24a provided in abutment 16 for the outflow of oil from chamber 12.

When the pressure acting on the end portion of sliding cap 9 is lower than the .pilot pressure Pc, sliding cap 9 and body 4 are at a distance from each other, as shown by FIG. 1, so that bearing surfaces 18 and 19 are respectvely at a distance from bearing surfaces and 21, the slots 22 for the inflow of oil and the annular space 24 for the outflow of oil being open.

On the other hand, when the pressure acting on the top of the end portion 10 0f sliding cap 9 is higher than said pressure P0, sliding cap 9 and body 4 are applied against each other as shown by FIG. 2. Bearing surfaces 18 and 19 come into contact with bearing surfaces 20 and 21 respectively, whereby the higher end of every slot 22 is closed by bearing surface 21 and annular space 24 is closed by bearing surface 20.

The axial effort between sliding cap 9 and body 4 is transmitted partly through the oil in chamber 12 and partly through the two films of oil formed respectively between bearing surfaces 18 and 20 and bearing surfaces I9 and 21.

Another embodiment of the invention according to FIG. 3 on which the reference numbers designate the same elements as on FIG. l will be hereinafter described:

Sliding cap 9 is axially guided by the cooperation of a portion of the inner wall of skirt 11 and of the outer wall of the upper portion of the skirt 6 of body 4.

Relative axial movement of sliding cap 9 away from body 4 with a shoulder 25 cooperoting with the lower part FIGS. 1 and 2. But relative axial movement of sliding cap 9 toward body 4 is limited by providing the skirt 6 of body 4 with a shoulder 25 cooperating with the lower part of the skirt 11 of sliding cap 9.

Oil under pressure is fed to chamber 12 through a plurality of inlet passages consisting of radial slots 26 located at the periphery of the portion 5 of body 4.

The inner ends of slots 26 open directly into chamber 12, while the outer ends thereof communicate with a groove 27 located in the inner wall of the skirt 11 of sliding cap 9 at the level of groove 23.

The oil outlet from chamber 12 consists of a vcalibrated orifice made, as in the embodiment above described, of an annular space 24 between projection 14 and central bore 15, axial projection 14 being provided with a shoulder 28 slidably guided in said central bore 15.

When the pressure acting on the top face of sliding cap 9 is lower than pressure P0, sliding cap 9 and body 4 are kept at a distance from each other, as shown by FIG. 3.

The outer end of every radial slot 26 is then located opposite groove 27 and thus the shoulder 28 of axial projection 14 is not engaged in central bore 15; radial slots 26 are cleared and permit oil to enter chamber 12, While annular space 24 is also cleared and permits oil to fiow out.

On the contrary, when the pressure acting on the top of the end 10 of slid-ing cap 9 is higher than pressure P0, sliding cap 9 and central bore 15 are pushed toward each other, as shown by FIG. 4. The outer end of every radial slot 26 is closed by the inner wall of the skirt 11 of sliding cap 9, and annular space 24 is closed by the shoulder 28 of axial projection 14.

In this embodiment, the axial force between sliding cap 9 and body 4 is entirely transmitted through the oil enclosed in chamber 12.l

For both of the embodiments above described, the distribution of the slots constituting the inlets of oil under pressure to chamber 12 (22 or 26) is a function of the thermal load, i.e. of the heat transmitted to the portion 10 of sliding cap 9.

Thus, FIG. 5 shows a diesel engine having a piston 1 provided with a cylinder head 3, said cylinder head 3 comprising a turbulence chamber 29 and a transfer passage 30. The inlet orifices are slots 22, the area of working portion 10 located opposite passage 30 will support a very important thermal load. To reduce this, a great number of inlet orifices are provided in this area of working portion 10. About 70% of the flow rate of oil under Ipressure is fed through the inlet orifices located in said area of working portion 10, while about 30% are distributed regularly at the periphery of said work-ing portion 10.

According to the invention, body 4 is made of a light alloy, preferably chosen among alloys containing an irnportant proportion of silicon and more particularly of an alloy designated by the trademark AS 12 UN and which contains 12.50% of silicon, 1.50% of copper, 1.25% of nickel, 74.75% of iron and the remainder aluminum.

Sliding cap 9 is made of a metallic alloy resistant to high temperatures because such an alloy is carried to about 400 C. on every cycle. Said alloy is chosen among austenetic steels or refractory steels containing an important proportion of chromium, and in particular an alloy designated by the trademark SIMO and which contains 10% of chromium, 2.50% of silicon, 0.80% of molybdenum, 0.80% of manganese, 0.40% of carbon and the remainder iron.

Sliding cap 9 is guided through guiding surfaces 31, at least some of which are separated from one another by distributing grooves 32 adapted to receive the cooling liquid in circulation.

The circulation of the cooling oil considerably reduces the heating of sliding cap 9.

FIGS. 1, 3 and 6` show, at the level of the upper part of the outer face of skirt 6 of central body 4, two distribution grooves 32 located on either side of guiding surface 31 and connected with each other through a plurality of passages 33 (FIG. 6).

It should be pointed out that, in the two embodiments of FIGS. l-2 and FIGS. 3-4, respectively, the upper distribution groove 32 consists of groove 23. In the embodiment of FIGS. 1-2 the lower end of every slot 21 opens i-nto this groove 23. In the embodiment of FIGS. 3-4, complementary groove 27 into which opens lthe outer end of every slot 26 opens into this groove 23.

In all the embodiments above described a packing member 24 is provided between the lower groove 32 and the skirt of sliding cap 9.

In order to improve the distribution of oil, at least some of passages 33 are disposed in checkered relation with slots 22 or 26.

Conduit means are provided to connect a circulation pump delivering oil under pressure at a fixed flow rate to the llower distribution groove 32, said conduit means comprismg:

A set of conduits, not shown on the drawings, which lead oil under pressure from said pump to a channel 35 provided in connecting rod 7,

A distribution groove 36 provided at the end of connecting rod 7,

A distribution orifice 37 delivering oil to the inside of the hollow gudgeon pin 8 closed at both of its two ends respectively by two plugs 38 and prevented from pivoting i-n body 4 by a screw 39,

Two orifices 40 provided in gudgeon pin 8 near the two ends thereof and directed toward the upper part of piston 1,

Two axial conduits 41 extending axially in body 4 from orifice 40 approximately to the lower distribution groove 32,

And, iinally, two radial conduits 42 connecting the lower distribution groove with axial conduits 41, respectively.

The circulation of oil, when the pressure inthe cylinder is lower than pressure P0, has the direction indicated by the arrows of FIGS. 1 and 3.

Pressure P.o depends mainly, on the one hand, on the pressure P of oil in chamber 12, and, on the other hand, on the ratio of the surfaces respectively subjected to said pressure P and to the pressure in cylinder 2.

For example, when pressure P is equal to about 5 kg./cm.2 the pressure P0 will be about 4 kg./cm.2.

Concerning a four-stroke diesel engine, the circulation of oil takes place,

During all the time of admission,

During the beginning of the compression time,

And during nearly all the exhaust time.

Finally, the amount of oil enclosed in chamber 12 prevents high temperatures. In fact the admission temperature of oil in chamber 12 is relatively low (about 80 C.), with respect to the mean pressure of the working portion of sliding cap 9 (about 250 C.).

A piston according to the invention has many advantages:

As the sliding cap supports the most important thermic loads, it is cooled by an oil circulation which has for its effect to increase the life of the piston and cylinder unit and to ensure a good mechanical behaviour of the sliding Cap;

The central body is insulated thermally from the sliding cap by a cushion and a tilm of oil;

Finally, the axial forces are transmitted between the sliding cap and the central body through a cushion of oil which has for its effect considerably to reduce the loads supported by the connecting rod during the motor stroke.

While the above description discloses what are deemed to be practical and etlicient embodiments of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts, without departing from the principle of the invention as comprehended within the scope of the appended claims.

What I claim is:

1. An internal combustion engine having a pressurized oil lubricating system, which comprises, in combination,

a cylinder,

a piston cap element slidable axially in said cylinder,

a piston body element slidable axially in said cylinder,

said piston elements having respective cooperating cylindrical side walls fitting slidably with respect to each other and Ibeing shaped to limit between their end walls a chamber of variable volume,

means for limiting the axial displacements of said piston cap element away from said piston body element,

a gudgeon pin carried by said piston body element, said gudgeon pin being providedwith an inner recess,

a connecting rod pivotally connected with said gudgeon pin for reciprocating said piston body element in said cylinder, said connecting rod being provided with a lubricating oil inlet conduit opening into said gudgeon pin recess,

said piston body element being provided with lubricating oil distribution conduits in communication at one end with said gudgeon pin recess and opening at the other end into the cylindrical side wall of said piston body element that cooperates with said piston cap element cylindrical wall, lubricating oil inlet and outlet means for said chamber,

the respective cooperating walls of said piston elements being adapted on the one hand to close said inlet and outlet means and said chamber in a uidtight manner when said piston cap element is brought into its position nearest to said piston body element by the pressure in said cylinder and on the other hand, when said piston cap element moves away from said piston body element assisted by the pressure of said lubricating oil, to open said inlet and outlet means and thereby connect a point of said chamber with the second mentioned ends of said oil distribution conduits and another point of said chamber with said lubricating oil outlet means.

2. An engine according to claim 1, wherein said piston body element is provided with a central bore and said piston cap element includes an axial projection extending into said central bore, said engine further comprising an abutment fixed to said axial projection and adapted to cooperate with said piston body element to limit the displacement of said piston cap element away from said piston body element.

3. An engine according to claim 1, wherein said piston body element comprises a iiat circular end portion and a cylindrical skirt and the outer face of said flat end portion is provided with two annular and concentric bearing surfaces located respectively in the central portion of said piston body element and at the periphery thereof, and wherein said piston cap element comprises a circular end working portion and a cylindrical skirt and the inner face of said circular working portion is provided with two annular and concentric bearing surfaces, an inner one and an outer one, located respectively opposite the two bearing surfaces provided on said outer face of said piston body element flat end portion, whereby the displacements of said piston cap element toward said piston body element are limited by the contact of said respective bearing surfaces with one another.

4. An engine according to claim 3, wherein the cylindrical wall of said piston body element is provided on the one hand with an annular groove in communication With said oil distribution conduits and on the other hand with longitudinally extending slots extending from said annular groove and ending opposite said outer bearing surface of said piston cap element.

5. An engine according to claim 2, wherein an annular space is provided between said projection and the wall of said central bore, said abutment being provided with orices extending throughout it and in communication with said annular space.

6. An engine according to claim 2, wherein the skirt of said piston body element includes a shoulder adapted to cooperate with the edge of the skirt of said piston cap element to limit the displacements of said piston cap element toward said piston body element.

7. An engine according to claim 6, wherein the inner wall of the skirt of said piston cap element is provided with an annular groove and wherein said piston body element comprises a flat circular end portion and a cylindrical skirt, the edge of the periphery of said piston body element end portion being provided with radial notches, said radial notches being so dimensioned as to have their inner ends always located in said chamber between said piston body element and said piston cap element and their outer ends tightly applied against the inner wall of said piston cap element skirt when said piston cap element is moved toward said piston body element, said outer ends being adapted to open into said annular groove when said piston cap element is moved away from said piston body.

8. An engine according to claim 5, wherein said projection includes a shoulder adapted to tit slidably in said central bore when said piston cap element is moved toward said piston body but to be clear of said bore when said piston cap element is at the maximum distance from said piston body element.

9. An engine according to claim 1, wherein said piston body element and said piston cap element are respectively made of a light alloy and a metal capable of resisting high temperatures, said piston body element being provided with at least two guiding surfaces between which are provided distribution grooves, said distribution 7 grooves communicating with said lubricating oil distribution conduits. t

10. An engine according to claim 9, wherein said pistonbody element includes a skirt, the upper portion of said skirt being provided with two distribution grooves located on opposite sides, respectively, of one of said guiding surfaces, the latter being provided with a plurality of longitudinal passages for connecting together said distribution grooves.

C) References Cited UNITED STATES PATENTS 11/1959 Mansfield 123-48 3,038,458 6/1962 Mansiield 12S-'78 3,161,112 12/1964 Wallace et al. 123-48 X 3,205,878 9/1965 Timour et a1 123--48 WENDELL E. BURNS, Primary Examiner. 

1. AN INTERNAL COMBUSTION ENGINE HAVING A PRESSURIZED OIL LUBRICATING SYSTEM, WHICH COMPRISES, IN COMBINATION, A CYLINDER, A PISTON CAP ELEMENT SLIDABLE AXIALLY IN SAID CYLINDER, A PISTON BODY ELEMENT SLIDABLE IN SAID CYLINDER, SAID PISTON ELEMENTS HAVING RESPECTIVE COOPERATINGG CYLINDRICAL SIDE WALLS FITTING SLIDABLY WITH RESPECT TO EACH OTHER AND BEING SHAPED TO LIMIT BETWEEN THEIR END WALLS A CHAMBER OF VARIABLE VOLUME, MEANS FOR LIMITING THE AXIAL DISPLACEMENTS OF SAID PISTON CAP ELEMENT AWAY FROM SAID PISTON BODY ELEMENT, A GUDGEON PIN CARRIED BY SAID PISTON BODY ELEMENT, SAID GUDGEON PIN BEING PROVIDED WITH AN INNER RECESS, A CONNECTING ROD PIVOTALLY CONNECTED WITH SAID GUDGEON PIN FOR RECIPROCATING SAID PISTON BODY ELEMENT IN SAID CYLINDER, SAID CONNECTING ROD BEING PROVIDED WITH A LUBRICATING OIL INLET CONDUIT OPENING INTO SAID GUDGEON PIN RECESS, SAID PISTON BODY ELEMENT BEING PROVIDED WITH LUBRICATING OIL DISTRIBUTION CONDUITS IN COMMUNICATION AT ONE END WITH SAID GUDGEON PIN RECESS AND OPENING AT THE OTHER END INTO THE CYLINDRICAL SIDE WALL OF SAID PISTON BODY ELEMENT THAT COOPERATES WITH SAID PISTON CAP ELEMENT CYLINDRICAL WALL, LUBRICATING OIL INLET AND OUTLET MEANS FOR SAID CHAMBER, THE RESPECTIVE COOPERATING WALLS OF SAID PISTON ELEMENTS BEING ADAPTED ON THE ONE HAND TO CLOSE SAID INLET AND OUTLET MEANS AND SAID CHAMBER IN A FLUIDTIGHT MANNER WHEN SAID PISTON CAP ELEMENT IS BROUGHT INTO ITS POSITION NEAREST TO SAID PISTON BODY ELEMENT BY THE PRESSURE IN SAID CYLINDER AND ON THE OTHER HAND, WHEN SAID PISTON CAP ELEMENT MOVES AWAY FROM SAID PISTON BODY ELEMENT ASSISTED BY THE PRESSURE OF SAID LUBRICATING OIL, TO OPEN SAID INLET AND OUTLET MEANS AND THEREBY CONNECT A POINT OF SAID CHAMBER WITH THE SECOND MENTIONED ENDS OF SAID OIL DISTRIBUTION CONDUITS AND ANOTHER POINT OF SAID CHAMBER WITH SAID LUBRICATING OIL OUTLET MEANS. 